C78-44 Primary Pulmonary Adenocarcinoma Presenting as Massive Recurrent Pleural Effusion: A Diagnostic Challenge

Abstract Introduction Non-Small Cell Lung Carcinoma (NSCLC) accounts for approximately 75-80% of all lung cancers, with adenocarcinoma being the most frequent histologic subtype. Malignant pleural effusion (MPE) often indicates advanced disease and is associated with poor prognosis. Recurrent pleural effusions that are refractory to medical therapy should raise suspicion of an underlying malignancy. We present a case of primary pulmonary adenocarcinoma manifesting with massive recurrent pleural effusion, highlighting the diagnostic and management challenges encountered. Case Report A 54-year-old male presented with progressive shortness of breath, cough with expectoration, hemoptysis, and intermittent chest pain over two months. Initial examination revealed decreased breath sounds and dullness to percussion over the left lower lung field. Chest radiography demonstrated massive left pleural effusion (∼1800 mL). Pleural fluid cytology revealed predominantly lymphocytic exudate with clusters of atypical glandular cells. Cell block sections showed hyperchromatic, enlarged nuclei and prominent nucleoli, consistent with adenocarcinoma.High-resolution CT of the thorax revealed a 90 × 75 mm soft-tissue lesion in the left lower lobe with multiple well-defined nodules in both lungs, bilateral pleural thickening, and loculated effusion. Pleural biopsy showed malignant glandular structures lined by dysplastic columnar epithelium with desmoplastic stroma. Immunohistochemistry demonstrated TTF-1 positivity and Thyroglobulin negativity, confirming the diagnosis of primary pulmonary adenocarcinoma. Discussion and novelty of the case Pulmonary adenocarcinoma frequently involves the pleura, and MPE often signifies tumor progression or metastasis. Vascular endothelial growth factor (VEGF)- mediated permeability and angiogenesis play key roles in MPE pathophysiology. The patient’s presentation with recurrent, rapidly accumulating pleural effusion underscores the aggressive nature of pleural metastasis. Diagnosis requires integration of imaging, cytology, histopathology, and immunohistochemistry. Accurate staging based on the TNM system is crucial for prognostication and treatment planning. Conclusion Recurrent MPE in adenocarcinoma portends poor prognosis, with 5-year survival rates under 15% in advanced disease. Management focuses on palliation through pleurodesis, systemic therapy, or indwelling pleural catheters. Early recognition of malignant effusion as a sign of underlying adenocarcinoma is vital for timely intervention and improved quality of life. This abstract is funded by: none